In recent years, research and development are energetically made on electrophotographic photosensitive members (organic electrophotographic photosensitive members) making use of organic photoconductive materials.
The electrophotographic photosensitive member is basically constituted of a support and a photosensitive layer formed on the support. In the present state of affairs, however, various layers are often formed between the support and the photosensitive layer for the purposes of, e.g., covering any defects of the surface of the support, protecting the photosensitive layer from any electrical breakdown, improving its charging performance, improving the blocking of injection of electric charges from the support into the photosensitive layer, and so forth.
Among such layers formed between the support and the photosensitive layer, a layer containing metal oxide particles is known as the layer formed for the purpose of covering any defects of the surface of the support. The layer containing metal oxide particles commonly has a higher electrical conductivity than a layer not containing any metal oxide particles (e.g., 5.0×108 to 1.0×1013 Ω·cm as volume resistivity). Thus, even where it is formed in a large layer thickness, any residual potential at the time of image formation can not easily come to increase, and hence any defects of the support surface can be covered with ease.
The covering of defects of the support surface by providing between the support and the photosensitive layer such a layer having a higher electrical conductivity (hereinafter “conductive layer) makes the support surface have a great tolerance for its defects. As the results, this makes the support have a vastly great tolerance for its use, and hence brings an advantage that the electrophotographic photosensitive member can be improved in productivity.
Patent Literature 1 discloses a technique in which tin oxide particles doped with phosphorus are used in a layer formed between the support and the photosensitive layer. Patent Literature 2 also discloses a technique in which tin oxide particles doped with tungsten are used in a protective layer formed on the photosensitive layer. Patent Literature 3 still also discloses a technique in which titanium oxide particles coated with oxygen deficient tin oxide are used in a conductive layer formed between the support and the photosensitive layer. Patent Literatures 4 and 5 still also disclose a technique in which barium sulfate particles coated with tin oxide are used in a layer formed between the support and the photosensitive layer. Patent Literature 6 still also discloses a technique in which titanium oxide particles coated with indium oxide doped with tin (indium oxide-tin oxide) are used in a layer formed between the support and the photosensitive layer.